I've been using Arduinos for a couple of years now (Uno, Due, Nano,...).I recently got two new Arduino Nano V3 from SainSmart (via Amazon).I hooked them to the computer, and everything seemed to be working fine on the first connection.The computer recognized the device and I was able to upload a simple program to the device.However, when I attempted to upload another program, I suddenly got the avr_dude sync error.I unplugged the device and plugged it back to the computer, and since then, the computer refuses to recognize the device.Under device manager, I see under "Other Devices", "FT232R USB UART". All attempts to update the driver to the latest FTDI drivers fail ("Windows was unable to install your FT232R USB UART"). This was replicated on two computers (windows 7, 8.1, both x64, and both are able to recognize other arduinos, like my Due).I have the suspicion that something got damaged during the first connection to the computer, but I have no way to know for sure.This exact scenario was replicated with the second Nano I got. First time I connected it, everything worked. All subsequent attempts to connect to the device fail.

No wires were connected to the arduino, so this can't be some short-circuit problem. The same USB cable works with my Due, so it isn't a cable problem.

Interesting. It is good to know I'm not the only one who experienced this problem.I wrote to SainSmart. Let's see what they say. I hope they can reproduce the problem on their side as well.If you have time to test the Oct 1st hypothesis, it would be great.Were your boards also manufactured by SainSmart, or by other third party company?